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Search Results: 1 - 10 of 462966 matches for " A. Mitra "
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Role of anti-depressant fluoxetine in the puva treatment of psoriasis vulgaris
Mitra A
Indian Journal of Dermatology, Venereology and Leprology , 2001,
Abstract: Severity of psoriasis vulgaris is known to be modified by psychological stress. The objective of this study was to evaluate the role of fluoxetine in the PU VA treatment of psoriasis. Twenty patients with progressive disease having more than thirty per cent body area involvement were included in a randomized, double blinded, placebo- controlled, age and sex matched study. All patients were on PUVA treatment, half of patients were given fluoxetine 20 mgs daily whereas the ten were given placebo. Assessment was done by Psoriasis Area and Severity Index (PASI) scoring after every 5 exposures of PUVA treatment till 20 treatments. All ten patients who took fluoxetine along with PUVA treatment showed better response and quicker remission. Fluoxetine may be used as an adjuvant in PUVA treatment of psoriasis.
Can magnetism-assisted quasiperiodic structures in Russell-FeS `bubbles' offer a quantum coherent origin of life?
Gargi Mitra--Delmotte,A. N. Mitra
Physics , 2007,
Abstract: This paper seeks to expand the scope of the alkaline seepage site hydrothermal mound scenario of Russell et al, by appealing to its wider canvas for hypothesizing self-assembly of gregite clusters via interplay of forces within the gel phase of FeS membranes: directed heat transport a la Rayleigh-Benard convection for dissociation, vs oriented attachment (small clusters) and magnetic forces (large clusters) for association, the latter assisted by magnetic mound constituents. The directed movement of tiny clusters through cluster layers are reminiscent of processes like budding, molecular motors, pre-RNA world on the lines of Cairns-Smith's hypothesis, and optical polarity. Higher rate of (soft) multinucleate formation vs growth rate of (rigid) microcrystals, correlates with icosahedral (forbidden crystallographically!) framboidal morphology. This pattern indicates a link to phylotaxis, thus reinforcing the quasi-periodicity connection which can provide a natural access to features like surface limit, anomalous transport and low thermal conductivity, while facilitating diffusion through clusters. And magnetism offers a hierarchy of features: primordial multicellularity; phase correlations of assembled molecules; overcoming thermal decoherence. These dynamical nested structures offer possibilities for iterative computations, adaptive learning, and coherent quantum searches. The link between enzymatic FeS clusters and the Hadean ocean floor is seen as part of a larger conceptual framework uncovering a role for Magnetism and the Origin of Life.
Magnetism, FeS colloids, and Origins of Life
Gargi Mitra-Delmotte,A. N. Mitra
Physics , 2008, DOI: 10.1007/978-1-4419-6263-8_31
Abstract: A number of features of living systems: reversible interactions and weak bonds underlying motor-dynamics; gel-sol transitions; cellular connected fractal organization; asymmetry in interactions and organization; quantum coherent phenomena; to name some, can have a natural accounting via $physical$ interactions, which we therefore seek to incorporate by expanding the horizons of `chemistry-only' approaches to the origins of life. It is suggested that the magnetic 'face' of the minerals from the inorganic world, recognized to have played a pivotal role in initiating Life, may throw light on some of these issues. A magnetic environment in the form of rocks in the Hadean Ocean could have enabled the accretion and therefore an ordered confinement of super-paramagnetic colloids within a structured phase. A moderate H-field can help magnetic nano-particles to not only overcome thermal fluctuations but also harness them. Such controlled dynamics brings in the possibility of accessing quantum effects, which together with frustrations in magnetic ordering and hysteresis (a natural mechanism for a primitive memory) could throw light on the birth of biological information which, as Abel argues, requires a combination of order and complexity. This scenario gains strength from observations of scale-free framboidal forms of the greigite mineral, with a magnetic basis of assembly. And greigite's metabolic potential plays a key role in the mound scenario of Russell and coworkers-an expansion of which is suggested for including magnetism.
Magnetism, entropy, and the first nano-machines
Gargi Mitra-Delmotte,A. N. Mitra
Physics , 2009, DOI: 10.2478/s11534-009-0143-4
Abstract: The efficiency of bio-molecular motors stems from reversible interactions $\sim$ $k_B T$; weak bonds stabilizing intermediate states (enabling $direct$ conversion of chemical into mechanical energy). For their (unknown) origins, we suggest that a magnetically structured phase (MSP) formed via accretion of super-paramagnetic particles (S-PPs) by magnetic rocks on the Hadean Ocean floor had hosted motor-like diffusion of ligand-bound S-PPs through its template-layers; its ramifications range from optical activity to quantum coherence. A gentle flux gradient offers both detailed-balance breaking non-equilibrium and $asymmetry$ to a magnetic dipole, undergoing infinitesimal spin-alignment changes. Periodic perturbation of this background by local H-fields of template-partners can lead to periodic high and low-template affinity states, due to the dipole's magnetic degree of freedom. An accompanying magnetocaloric effect allows interchange between system-entropy and bath temperature. We speculate on a magnetic reproducer in a setting close to the mound-scenario of Russell and coworkers that could evolve bio- ratchets.
Consciousness: A Direct Link with Life's Origin?
A. N. Mitra,Gargi Mitra-Delmotte
Quantitative Biology , 2011,
Abstract: Inspired by the Penrose-Hameroff thesis, we are intuitively led to examine an intriguing correspondence of 'induction' (by fields), with the complex phenomenon of (metabolism-sustained) consciousness: Did sequences of associated induction patterns in field-susceptible biomatter have simpler beginnings?
Field-control, phase-transitions, and life's emergence
Gargi Mitra-Delmotte,A. N. Mitra
Quantitative Biology , 2012,
Abstract: Instances of critical-like characteristics in living systems at each organizational level as well as the spontaneous emergence of computation (Langton), indicate the relevance of self-organized criticality (SOC). But extrapolating complex bio-systems to life's origins, brings up a paradox: how could simple organics--lacking the 'soft matter' response properties of today's bio-molecules--have dissipated energy from primordial reactions in a controlled manner for their 'ordering'? Nevertheless, a causal link of life's macroscopic irreversible dynamics to the microscopic reversible laws of statistical mechanics is indicated via the 'functional-takeover' of a soft magnetic scaffold by organics (c.f. Cairns-Smith's 'crystal-scaffold'). A field-controlled structure offers a mechanism for bootstrapping--bottom-up assembly with top-down control: its super-paramagnetic components obey reversible dynamics, but its dissipation of H-field energy for aggregation breaks time-reversal symmetry. The responsive adjustments of the controlled (host) mineral system to environmental changes would bring about mutual coupling between random organic sets supported by it; here the generation of long-range correlations within organic (guest) networks could include SOC-like mechanisms. And, such cooperative adjustments enable the selection of the functional configuration by altering the inorganic network's capacity to assist a spontaneous process. A non-equilibrium dynamics could now drive the kinetically-oriented system towards a series of phase-transitions with appropriate organic replacements 'taking-over' its functions.
Spin Dynamics Of $qqq$ Wave Function On Light Front In High Momentum Limit Of QCD : Role Of $qqq$ Force
Mitra, A. N.
High Energy Physics - Phenomenology , 2007, DOI: 10.1016/j.aop.2007.05.008
Abstract: The contribution of a spin-rich $qqq$ force (in conjunction with pairwise $qq$ forces) to the analytical structure of the $qqq$ wave function is worked out in the high momentum regime of QCD where the confining interaction may be ignored, so that the dominant effect is $Coulombic$. A distinctive feature of this study is that the spin-rich $qqq$ force is generated by a $ggg$ vertex (a genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on as many quark lines, giving rise to a (Mercedes-Benz type) $Y$-shaped diagram. The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these ingredients, the differential equation for the 3D wave function $\phi$ receives well-defined contributions from the $qq$ and $qqq$ forces. In particular a $negative$ eigenvalue of the spin operator $i \sigma_1.\sigma_2\times \sigma_3$ which is an integral part of the $qqq$ force, causes a characteristic singularity in the differential equation, signalling the dynamical effect of a spin-rich $qqq$ force not yet considered in the literature. The potentially crucial role of this interesting effect vis-a-vis the so-called `spin anomaly' of the proton, is a subject of considerable physical interest.
Changes in cosmic ray cut-off rigidities due to secular variations of the geomagnetic field
A. Bhattacharyya,B. Mitra
Annales Geophysicae (ANGEO) , 2003,
Abstract: An analytical expression is derived for the cutoff rigidity of cosmic rays arriving at a point in an arbitrary direction, when the main geomagnetic field is approximated by that of an eccentric dipole. This expression is used to determine changes in geomagnetic cutoffs due to secular variation of the geomagnetic field since 1835. Effects of westward drift of the quadrupole field and decrease in the effective dipole moment are seen in the isorigidity contours. On account of the immense computer time required to determine the cutoff rigidities more accurately using the particle trajectory tracing technique, the present formulation may be useful in estimating the transmission factor of the geomagnetic field in cosmic ray studies, modulation of cosmogenic isotope production by geomagnetic secular variation, and the contribution of geomagnetic field variation to long term changes in climate through cosmic ray related modulation of the current flow in the global electric circuit.
A comment on black hole state counting in loop quantum gravity
A. Ghosh,P. Mitra
Physics , 2008,
Abstract: There are two ways of counting microscopic states of black holes in loop quantum gravity, one counting all allowed spin network labels $j,m$ and the other involving only the labels $m$. Counting states with $|m|=j$, as done in a recent Letter, does not follow either.
Entropy of Extremal Black Hole Solutions of String Theory
A. Ghosh,P. Mitra
Physics , 1995,
Abstract: For extremal black holes, the thermodynamic entropy is not proportional to the area. The general form allowed by thermodynamics is worked out for three classes of extremal black hole solutions of string theory and shown to be consistent with the entropy calculated from the density of elementary string states. On the other hand, the entanglement entropy does not in general agree with these results.
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